Ericsson WCDMA/HSDPA User Manual

Configuration and Management 

From a security perspective, certain Internet applications, for example FTP 
applications that open additional ports upon transfer, are especially 
problematic to handle. An Application Level Gateway (ALG) provides a 
translation and transportation service for such a specific application. 
Incoming data packets are checked against existing NAT and packet 
filtering rules, IP addresses are evaluated and a detailed packet analysis is 
performed. If necessary, the contents of a packet are modified and if a 
secondary port is required, the ALG will open one. The Ericsson W20 
includes ALG support for the following applications:  
 

File Transfer Protocol (FTP) 

TCP 

21 

Trivial File Transfer Protocol (TFTP) 

UDP 

69 

 
The ALG for each application does not require additional configuration. The 
supported ALGs can be enabled and disabled individually. To disable an 
ALG, clear the corresponding check box on the NAT page and click 

.

Port forwarding is used to allow incoming access to a specific local network 
device, for example an internal web server. 

Note:  Port forwarding requires a public IP address of the Ericsson W20. 

The Ericsson W20 IP address is displayed on the Internet page. If 
the IP address begins with 10, 172, or 192, it is probably private. 
In this case, no incoming access from the Internet is allowed. For 
more information on public and private IP addresses, contact your 
service provider. 

To add a new port forwarding instance, click Add instance in the Port 
Forwarding section on the NAT page. The Add Port Forwarding page is 
displayed: 

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